Biopharmaceutical products, such as monoclonal antibodies, recombinant proteins, vaccines, blood derivatives and animal products carry a risk of transmitting infectious viruses. This is due to source material possibly being intrinsically contaminated with viruses. Additionally, manufacturing processes of biopharmaceutical products are susceptible to virus contamination from extrinsic sources. As a result, manufacturers of biopharmaceutical products are required to incorporate sufficient virus clearance steps into their manufacturing processes to ensure that their products are contaminant virus-free. It is a safety and regulatory imperative that manufacturing processes of biopharmaceutical products incorporate these virus clearance steps.
Evaluation of virus clearance step effectiveness in the manufacturing process is necessary. The purpose of virus clearance evaluation is to assess the capability of a manufacturing production process to inactivate and/or remove potential virus contaminants. Spiking studies are typically used to evaluate and validate virus clearance steps in a scaled down model of a production-scale process. However, the purity and titer of virus stocks used for virus clearance studies have a significant influence on study outcome. The purity and titer of the virus stocks impact how well the scaled down model represents the production-scale process.
For example, impurities in virus stocks adversely impact the testing of small virus retentive filters used in virus clearance steps. The impurities are introduced as a consequence of the impure virus stock used in the validating spiking studies, and are not reflective of typical manufacturing processes on the production-scale process. As a result of the impurities, the test unit (e.g., a filter) fouls prematurely, exhibits altered fouling conditions, and adversely affects fluid passage through the virus filter. Consequently, the true throughput capacity of the filter is underestimated, which in turn leads to the inappropriate sizing of the production scale-unit. As a result, the production-scale unit is oversized to compensate for the apparent lower performance of the unit in the validation study. This increases production costs. In addition, this underestimates the actual capacity of the test unit to clear virus in the production process since the titer of the virus stock often determines the maximum possible concentration of virus spiked into the test material which, when all virus is effectively cleared by the test unit, limits the virus clearance claim of the test unit.
Current methods of producing virus stocks (e.g., for use in spiking studies) lack the capacity to produce virus stocks with low impurity content. Furthermore, virus stocks of as high titer as possible are desirable, since the volume of virus spike that can be added to a test system is limited by Regulatory Guidelines. Current methods lack the capacity to produce virus stocks of high titer and high purity. Thus, a need exists for methods of preparing virus stocks with high purity, as well as high titer.